LT1763CS8-5#PBF Linear Technology, LT1763CS8-5#PBF Datasheet - Page 18

• Manufacturer Part Number: LT1763CS8-5#PBF
• Description: IC REG LDO 500MA 5V MCRPWR 8SOIC
• Manufacturer: Linear Technology

Specifications of LT1763CS8-5#PBF

• Regulator Topology: Positive Fixed
• Voltage - Output: 5V
• Voltage - Input: Up to 20V
• Voltage - Dropout (typical): 0.3V @ 500mA
• Number Of Regulators: 1
• Current - Output: 500mA
• Current - Limit (min): 520mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Primary Input Voltage: 20V
• Output Voltage Fixed: 5V
• Dropout Voltage Vdo: 300mV
• No. Of Pins: 8
• Output Current: 500mA
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LT1763 Series
Table 2. SO-8 Package, 8-Lead SO
* Device is mounted on topside
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input voltage
range of 4V to 6V, an output current range of 0mA to 250mA
and a maximum ambient temperature of 50°C, what will
the maximum junction temperature be?
The power dissipated by the device will be equal to:
where,
So,
The thermal resistance will be in the range of 60°C/W to
86°C/W, depending on the copper area. So, the junction
temperature rise above ambient will be approximately
equal to:
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature, or :
18
TOPSIDE*
2500mm
1000mm
225mm
100mm
50mm
I
I
V
I
P = 250mA(6V – 3.3V) + 5mA(6V) = 0.71W
0.71W(75°C/W) = 53.3°C
T
OUT(MAX)
OUT(MAX)
GND
JMAX
IN(MAX)
COPPER AREA
2
2
2
at (I
2
2
= 50°C + 53.3°C = 103.3°C
BACKSIDE
= 6V
OUT
2500mm
2500mm
2500mm
2500mm
2500mm
(V
= 250mA
IN(MAX)
= 250mA, V
2
2
2
2
2
– V
BOARD AREA
2500mm
2500mm
2500mm
2500mm
2500mm
OUT
IN
) + I
= 6V) = 5mA
2
2
2
2
2
GND
(JUNCTION-TO-AMBIENT)
THERMAL RESISTANCE
(V
IN(MAX)
60°C/W
60°C/W
68°C/W
74°C/W
86°C/W
)
Protection Features
The LT1763 regulators incorporate several protection
features which make them ideal for use in battery-powered
circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the devices are protected
against reverse input voltages, reverse output voltages
and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal operation,
the junction temperature should not exceed 125°C.
The input of the device will withstand reverse voltages of
20V. Current fl ow into the device will be limited to less
than 1mA (typically less than 100μA) and no negative
voltage will appear at the output. The device will protect
both itself and the load. This provides protection against
batteries which can be plugged in backward.
The output of the LT1763-X can be pulled below ground
without damaging the device. If the input is left open-circuit
or grounded, the output can be pulled below ground by
20V. For fi xed voltage versions, the output will act like a
large resistor, typically 500k or higher, limiting current fl ow
to less than 100μA. For adjustable versions, the output
will act like an open circuit; no current will fl ow out of the
pin. If the input is powered by a voltage source, the output
will source the short-circuit current of the device and will
protect itself by thermal limiting. In this case, grounding
the SHDN pin will turn off the device and stop the output
from sourcing the short-circuit current.
The ADJ pin of the adjustable device can be pulled above
or below ground by as much as 7V without damaging the
device. If the input is left open-circuit or grounded, the
ADJ pin will act like an open circuit when pulled below
ground and like a large resistor (typically 100k) in series
with a diode when pulled above ground.
In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp
voltage if the output is pulled high, the ADJ pin input current
must be limited to less than 5mA. For example, a resistor
divider is used to provide a regulated 1.5V output from the
1.22V reference when the output is forced to 20V.
1763fg